A liquid filling type pressure sensor in which a semiconductor type pressure detection device is accommodated inside a pressure receiving chamber partitioned by a diaphragm to be filled with oil has been used to detect a refrigerant pressure by being installed in a refrigerator-freezer or an air conditioner, or to detect a pressure of supplied oil by being installed in a fuel feeder of a vehicle.
The semiconductor type pressure detection device is disposed inside the pressure receiving chamber, and has a function of converting a pressure change inside a pressure receiving space into an electric signal and outputting the converted electric signal to the outside.
The diaphragm disposed inside the pressure receiving space includes a flexible metal plate. Thus, depending on a usage environment, when a potential difference is generated between a pressure detection element including a semiconductor and a metal housing, or when injected oil is charged due to static electricity, etc., an electric charge may stay on a surface of the pressure detection element, and thus a defect may be generated in a detection operation of the pressure detection element.
In this regard, there has been a known pressure sensor that attempts to resolve the defect by further disposing a discharging plate inside the pressure receiving space in which the pressure detection element is accommodated, and connecting the discharging plate to zero potential of an electric circuit (see Patent Document 1).